"But 51%er can turn dishonest at any moment, for there is a huge difference between someone who only holds 49% of the revenue, and someone who holds 51%. A 49%er can collect only 49% of the rewards if they are honest; if they engage in selfish mining, they can collect almost 100% of the rewards, but they cannot launch a full 51% attack. A 51%er can collect 100% of the mining rewards."

The article is wrong in general simply because there is no specific number that is important. It is a gradual change. "51% attack" is simple to say and became the common language used to describe the weakness. The higher one group goes, the more confirmations are needed to confirm mining and transactions because there is a higher and higher risk of doublespend and other consensus attacks succeeding for a given confirmation. We are at risk at 40% and at 60%, and technically the other percentages too.

I am pretty much regurgitating a reminder of this very fact from the front page of r/bitcoin this week.